1 Mhz Resonant Coil Setup

[Peterae]

So the race is on.

3 AA energizer batteries or 4.5 V DC Input

100 Watt Bulb as load.

Frequency of operation about 1MHz

Must be a resonant system to increase the power factor and drastically cut the input reactive resistance of an ordinary transformer.

We could call it a TPU  

Anyone fancy designing a circuit to try.

OR

is it as simple as placing a cap across a mains transformer primary and secondary and connecting the bulb across the secondary and cap

A pure reactance will not dissipate any power.

but how can you use a standard transformer if the resonant frequency is 1MHz surely we need an air transformer like Don used

My aim is to build a pocket version of Don's table top device, but driving the primary using a blocking oscillator.

[Peterae]

Construction and Test Data coming Soon

First Job was to build the primary resonant coil for 1Mhz Now Done

Then the next job was to buid a fet based Blocking oscillator to drive the above coil. Now Done.

Next up is the secondary and capture circuit. Not yet Done

[Peterae]

A picture of the blocking oscillator and 1.04Mhz Primary

[Peterae]

Scope shot from GND to Fet Drain.

Note amplitude is 248Volts and the Frequency is 1.04Mhz, the resonant frequency of the blocking oscillator is set by the tuned LC

[Peterae]

I am using my psu set to 125 Volts Current drawn is 6mA, i didn't want to go with the 5volts as above, i wanted to get a little closer to a tesla system but using an oscillator to drive the coil as large as i could.

Also note total power consumed is about 0.75 Watts

[Peterae]

Here's a FFT Shot of my scope probe laying near the primary coil.

[Peterae]

Here's the circuit

OOPS Note i missed out a 330K resistor in the original Circuit and C4 is 47nF not 470nF so i have uploaded the correct circuit now.

[Chet K]

Sir ,
I've been inviting guests .
I hope you don't mind?

Chet

[Peterae]

Hi Chet

No problem, thats why i document my builds whether successful or not, hopefully something can be learned along the way for others to build upon.

[Peterae]

My intention here with this build is to study Don Smiths setup and see what i get.

With Don's device there are 2 secondaries, one is parallel tuned, but the other has no tuning but goes straight to a diode we have always suspected that there maybe in part a component missing to deceive us from the correct function of this second coil.

Don refers to this coil as the current supply to the system.

It has occurred to me that maybe this second secondary coil is infact series tuned.

In a series RLC circuit at resonance, the current is limited only by the resistance of the circuit

An equal magnitude voltage will also be seen across the capacitor but in antiphase to the inductor. If R can be made sufficiently small, these voltages can be several times the input voltage. The voltage ratio is, in fact, the Q of the circuit

So it would be relatively easy to hide a capacitor in series with the secondary coil, and when tuned this indeed could provide the current aspect to the final output, also note he uses thick wire for his secondaries, now we know why.

Anyway just thinking out loud.
You heard it here first  , so 2 secondaries 1 parallel tuned one series tuned 

[Peterae]

Primary Coil details.

Wire Length = 430.8 cm
Coil Length = 29mm
Diameter = 16.5mm
Resistance @ 120Hz = 0.928R
Inductance = 49.95 uH
28 SWG Wire

For the secondary i want to use the magic 4* wire length which gives me 17.232 Meters
I will use a heavier wire maybe 22SWG

In which case i will aim for about 170uH which would require 137pf cap which will be good for using a low value trimmer for adjustment also.

[Peterae]

If anyone is going to try building the Blocking Oscillator use a pot first for the bias resistor chain, set this to turn the fet gate fully off by adjusting for low volts and then adjust up to find the point oscillation starts, if you dont do this then there is danger that the fet is biased on to much and when you apply 125 volts the fet will burn.

[ion]

Hi Peterae

Another trick I learned in building these oscillators is to add some resistance in series with the 10nf back to the gate so that when you hit the TVS diode conduction point you don't hog too much current out of the circuit.

This is important for blocking oscillators where high efficiency is required, if you don't care how much energy you burn in the "tickler" circuit then no problem.

As you may have seen in some of the circuits I have posted, I sometimes use a potentiometer divider to precisely adjust the feedback into the gate, rather than slamming it hard.

For a Don Smith circuit, this may not be an issue.

I have always liked playing with LC series circuits, and yes, the current can go to infinity in the ideal world.

Good luck

[Peterae]

Hi ION

I did try a 5k pot in series with the feedback cap but having already built a 1 turn pickup into the coil, i could not get any adjustment, as soon as i turned the 5k pot even slightly i could not get oscillation back, maybe in hind sight i should have used a few more turns and tried this.

Also interestingly the gate is held way lower than it's hard switch on point to stop excessive turn on current.

Thanks for the advice  

PS just ordered some 70pf trimmers for each secondary coil.


Peter

[Peterae]

A Scope shot of the gate notice the DC offset

[Peterae]

Here's an interesting thought.

Don's second coil fed a rectifier diode, which then connected to a capacitor bank, so would a series connected Inductor-Diode-Capacitor Bank constitute a series tuned resonant circuit. what effect would the diode have?

[ion]

Here's an interesting thought.

Don's second coil fed a rectifier diode, which then connected to a capacitor bank, so would a series connected Inductor-Diode-Capacitor Bank constitute a series tuned resonant circuit. what effect would the diode have?

The circuit as you described would probably not oscillate, as there is little to no current flowing in the reverse direction.

It would seem that in this case the diode capacitance would predominate in the reverse direction forcing a much higher frequency.

Still, it is an interesting idea. I once tried splitting a resonant tank into two separate inductors with  diodes. If i remember correctly it did resonate, but there were losses in the diodes.

[Peterae]

Thanks for the reply ION , i may carry out some tests at some point and try a few different permutations.
It was a bit of a long shot anyway as the cap bank is either 5 x 2uF or 5 x 8uF in parallel.

[giantkiller]

This puts the fet in linear operation mode. Of course I am preaching to the choir.
Nice sine output!
Saw that with the audio circuit I built from Bolt's suggestion for my Trinity hammer / 3 speaker canon.
Side note: I play Pied piper with a community of voles behind my backyard fence. I am watching for birth defects.

A Scope shot of the gate notice the DC offset

[Peterae]

Thanks gk

I have built one of the secondaries it came out @ 123.43uH
It uses exactly 4 times the wire length of the primary for the turns.

I am waiting on 2 x 70pF trimmers to arrive, using a 150pf cap across the secondary and the trimmer across this should give me an adjustment range of 970kHz to 1.17Mhz.


Coil uses 22SWG wire

[Peterae]

Having wound the last secondary coil i decided it was way too long, so i halved the wire length and then wound a new primary coil using a quarter of the primary wire length.

Primary Inductance is now 17.62uH
Secondary Inductance is 56.52uH

So new primary cap value will be 1.47nF
and secondary will be 440pf

I also made a new oscillator and cleaned this up using board, i will try a zener diode in place of the TVS Diode and reverse protection 1n4007 diode.

As you can see i still need to connect the board and check it's operation.

[BEP]

Peterae,

The best advice I can give you on simple RF tank circuits is the same info EM shot down as being incorrect. He cited the book but his book must have been several generations from the physical world.

For the best storage, use and exchange of energy between the capacitor and coil..... Think of the same simple LC circuit but put a transmission line between the L & C, for concept only.

The best operating LC tank circuit has matching 'at-frequency impedance' between the capacitor and inductor.

The book thumpers are quite correct in saying 'it doesn't matter'. It doesn't matter as long as you are not concerned with overly short oscillations due to energy loss in the tank circuit.

I communicate via PSK to Antarctica and South Africa on a regular basis with less than 1 watt using this understanding and the same long-wire antenna and tank circuit that charges my station batteries.


And no, simply adding a capacitor to a transformer has little to do with gain of the system. Otherwise, my main bench isolation transformer would be OU. Here is the schematic and photo of the strange winding arrangements.

[Peterae]

The best operating LC tank circuit has matching 'at-frequency impedance' between the capacitor and inductor.

So you are saying i should be matching the impedance of the capacitor and inductor at resonance.
I need to look at this then.

Thanks WW
PS that transformer is way over my head, i cannot understand why some windings are Open :

[Peterae]

So for the Primary @ 1 Mhz I Have

L = 17.62uH
C = 1.47nF

Xc = 1/(2 x pi x f x C)
Xc = 108.2687 Ohms

and

Xl = 2 x pi x f x L
Xl = 110.709 Ohms.

Wow don't ask me how, but it a fairly close match.

Secondary

L = 56.52uH
C = 440pf

Xc = 361.715 Ohms
Xl = 355.126 Ohms

thats pretty close as well, probably even closer if i allow for the trimmer to tune for the 1mhz resonance.

So how come they are close, is it becausewhen i used the resonant formulas to calculate my cap value for a given inductor that the impedance automatically gets figured into the equation.

[BEP]

The normal math will make it happen anyway. L & C will end up equal (but opposite).

Resistance will take up the differences you see, or make it worse  

Never mind. You were doing it right. I should have assumed you were doing it right